In a system which applies a torque-based control to a direct injection engine with a turbocharger and is capable of switching between stoichiometric running and lean-burn running in accordance with a driving state, in order to provide a means for obtaining preferred exhaust performance and driveability, a turbo lag index is computed on the basis of supercharged pressure information or air intake pipe pressure information which are obtained directly or indirectly, and then a throttle opening or a fuel injection quantity is corrected on the basis of the above-described turbo lag index to obtain desired torque and exhaust characteristics. As a result, it is possible to prevent a torque variation, a change in torque characteristics, exhaust deterioration, or the like in a transient time, which are generated due to a turbo lag.
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10. A control unit of an internal combustion engine, to which a throttle opening degree signal is input, and from which a fuel injection quantity signal is output, wherein
a supercharged pressure signal or an air intake pipe pressure signal is further input to the control unit, and the fuel injection quantity signal is varied so that the air-fuel ratio is maintained constant on the basis of the supercharged pressure signal or the air intake pipe pressure signal during an acceleration state in which the throttle opening degree signal is varied.
11. A control unit of an internal combustion engine, to which a signal concerning an air-fuel ratio is input, and from which a fuel injection quantity signal is output, wherein
a supercharged pressure signal or an air intake pipe pressure signal is further input to the control unit, so that the fuel injection quantity signal is varied in accordance with a pump loss change estimated on the basis of the supercharged pressure signal or the air intake pipe pressure signal during a transient state in which the air-fuel ratio signal is varied from a stoichiometric or rich state to a lean state.
13. A method for controlling an air precedence controlled turbocharger type of supercharged engine, in which a target fuel injection quantity of a fuel injection valve is determined so as to satisfy at least one of a target engine torque and a target air-fuel ratio, including the step of
correcting a fuel injection quantity in accordance with a pump loss change estimated on the basis of supercharged pressure information or air intake pipe pressure information which obtained directly or indirectly during a transient period in which an air-fuel ratio shifts from a stoichiometric or rich area to a lean area.
12. A method for controlling a fuel precedence controlled turbocharger type of supercharged engine, in which a target fuel injection quantity of a fuel injection valve is determined so as to satisfy at least one of a target engine torque and a target air-fuel ratio, including the steps of:
correcting a fuel injection quantity on the basis of supercharged pressure information or air intake pipe pressure information during a throttle opening degree is varied; and
correcting the fuel injection quantity, in a time of transition in which supercharging delay is generated, so that an air-fuel ratio is constant.
1. A control apparatus of an engine of a turbocharged lean-burn engine, which determines at least one of a target opening degree of a throttle valve and a target fuel injection quantity of a fuel injection valve on the basis of at least one of a target engine torque and a target air-fuel ratio, wherein
the fuel control apparatus is adapted to correct, during transient running status in which an opening degree of said throttle is varied, a fuel injection quantity of said fuel injection valve on the basis of at least one of supercharged pressure information and air intake pipe pressure information, characterized in that said transient running status corresponds to a status at an acceleration time, and a base fuel injection quantity is corrected, during the status, so that an air-fuel ratio is constant.
7. The control apparatus of an engine of a turbocharged lean-burn engine, which determines at least one of a target opening degree of a throttle valve and a target fuel injection quantity of a fuel injection valve on the basis of at least one of a target engine torque and a target air-fuel ratio, wherein
the fuel control apparatus is adapted to correct, during transient running status in which an opening degree of said throttle is varied, a fuel injection quantity of said fuel injection valve on the basis of at least one of supercharged pressure information and air intake pipe pressure information, characterized in that said transient running status corresponds to a running status in which the air-fuel ratio shifts from a stoichiometric or rich area to a lean area, and a base fuel injection quantity is corrected on the basis of a pump loss change estimated in the status.
2. The control apparatus of an engine of a turbocharged lean-burn engine, which determines at least one of a target opening degree of a throttle valve and a target fuel injection quantity of a fuel injection valve on the basis of at least one of a target engine torque and a target air-fuel ratio, wherein
the fuel control apparatus is adapted to correct, during transient running status in which an opening degree of said throttle is varied, a fuel injection quantity of said fuel injection valve on the basis of at least one of supercharged pressure information and air intake pipe pressure information, characterized in that a control which determines at least one of the target opening degree of the throttle valve and the target fuel injection quantity of the fuel injection valve so as to satisfy at least one of said target engine torque and said target air-fuel ratio is a fuel leading type of torque-based control, and that the fuel injection quantity is corrected, in a time of transition in which a supercharging delay is generated, so that the air-fuel ratio is constant.
8. A control apparatus of a turbocharger type of supercharged engine, controlling the engine by so-called air leading engine control, which apparatus calculates a target engine torque and a target fuel injection quantity corresponding thereto on the basis of an accelerator opening degree and an engine revolution speed, determines an appropriate throttle opening degree in consideration of said target fuel injection quantity and a target air-fuel ratio in order to achieve the target engine torque and the target fuel injection quantity, and after measuring a taken air quantity in accordance with the throttle opening degree, determines a base fuel injection quantity on the basis of the measured air quantity and the target air-fuel ratio to obtain a desired engine torque, characterized in that,
during a transient period in which an air-fuel ratio shifts from a stoichiometric or rich area to a lean area, said base fuel injection quantity is corrected in accordance with a pump loss change estimated on the basis of supercharged pressure information or air intake pipe pressure information which are obtained directly or indirectly.
3. The control apparatus of an engine according to
4. The control apparatus of an engine according to
5. The control apparatus of an engine according to
6. The control apparatus according to
9. The control apparatus of an engine according to
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1. Field of the Invention
The present invention relates to a control system of a gasoline engine for an automobile, and particularly to a control system of an engine with a supercharger.
2. Description of the Prior Art
With respect to a current gasoline engine system for an automobile, there are many kinds of engine bodies and engine controls for controlling the engine bodies, in correspondence with diversified needs.
As one type of the engine body, in addition to a general type of natural air intake engine in which the air is taken into a cylinder by utilizing a negative pressure generated when a piston moves down, an engine with a supercharger in which the air is forced into the cylinder by utilizing the supercharger to effect high output has been came into practical use. As a typical supercharger, there are a mechanical supercharger as shown in JP-A-10-274070 and a turbocharger as shown in JP-A-2001-82197. The former utilizes shaft output of an engine to drive a compressor, while the latter utilizes exhaust gas of an engine for the same purpose. At present, the mainstream of the supercharger is the turbocharger having a high energy efficiency.
As further type of the engine body, a cylinder injection engine in which the fuel is directly injected into a cylinder as shown in JP-A-10-47114 has been practically used, in stead of a conventional engine in which the fuel is injected into an air intake port. In the direct injection engine, ultra-lean-burn driving can be performed to improve fuel consumption due to reduction in a pump loss. Also, as shown in JP-A-2000-248978, if the direct injection engine and the turbocharger are combined together, it is possible to further increase the amount of an intake air even when the throttle has been fully opened, which results in an advantage of expanding a lean-burn area toward a high load side in comparison to the natural air intake engine. In addition, in the lean-burn driving, an exhaust gas quantity is substantially increased in comparison to the natural air intake engine so that the number of revolution of a turbine is increased, therefore it can be expected to improve a response of generating torque in correspondence with accelerator operation.
On the other hand, with respect to an engine control, a so-called torque-based (torque demand) control is practically used as a new logic engine control. The backgrounds of its development is: this control is essential in the above-described lean-burn system for reducing a torque variation generated when normal burn driving (hereafter referred to as stoichiometric driving) in which A/F is approximately 14.7 and lean-burn driving are switched; a torque required to an engine from outside thereof is increased, as shown in a traction control, and thus a processing part therefor is required; and an electrically controlled throttle as is a key device has been practically used. As a concrete control content, a target engine torque is set by comprehensively considering an idle requirement torque and an external requirement torque for a car body control and the like, as well as an accelerator operation of a driver, and a fuel injection quantity and an intake air quantity are controlled to achieve the target engine torque. Because the engine torque is largely dependent on the fuel injection quantity, a fuel control is important for achieving the target engine torque, while it is an essential requirement to match an air-fuel ratio to its desired value from the viewpoint of high efficiency utilization of a catalyst for cleaning exhaust gas. Thus, in this control, the compatibility of control accuracies of the fuel control and the air-fuel ratio control is important.
There are two types of methods proposed as torque-based controls, which are different from each other depending on determination ways of a fuel injection quantity. One type is an air leading (air precedence) type in which a fuel injection quantity is determined after a real intake air quantity is measured as shown in JP-A-10-89140, and the other type is a fuel leading (fuel precedence) type in which a fuel injection quantity is directly determined on the basis of a result of computing a target torque as shown in JP-A-1-313636.
In the air leading type of control, a target air quantity is computed on the basis of a result of computing a target torque, and then a target throttle opening is transmitted to an electrically controlled throttle in order to achieve the target air quantity. After a real air quantity taken into a cylinder according to the target throttle opening is measured with an air flow sensor or the like, a fuel injection quantity is determined on the basis of the real air quantity and a target air-fuel ratio. In this method, because the fuel injection quantity is determined on the basis of the real air quantity, the method is characterized in that an accuracy of the air-fuel ratio is ensured. However, because the fuel injection quantity, with which a torque is determined, is determined via the air quantity, a generated torque may be largely out of the target torque depending on an accuracy of the air quantity control.
On the other hand, in the case of the fuel leading type of control, a target fuel injection quantity and a target air quantity are determined to obtain a desired air-fuel ratio on the basis of a result of computing a target torque, and then the corresponding signals are transmitted to an injector and an electrically controlled throttle respectively. Therefore, there is a disadvantage that if both the fuel injection quantity and the air quantity are not achieved to be equal to their target values, a desired air-fuel ratio is not obtained. In particular, regarding the intake air quantity, it is difficult to match the real air quantity with the target air quantity, therefore an improvement in the accuracy of the air quantity control is a large problem. However, it is characteristic that an accuracy of the torque control is high, because the result of target torque computation is directly reflected in the fuel injection quantity.
Accordingly, a system combining the above described several technologies, that is, a system which applies a torque-based control to a direct injection engine with a turbocharger and can switch stoichiometric driving and lean-burn driving in accordance with driving states is promising in view of improvement in fuel consumption, output, drivability, and the like.
However, in the case of the engine with the turbocharger, under a drive condition in which a throttle is rapidly opened such as in acceleration, it takes some time until the turbine revolution number increases because of inertial of the turbine, which causes a phenomenon in which it takes a certain time until a supercharging pressure reaches to its target value, that is, causes a turbo lag. This occurs remarkably in acceleration from a low revolution and low load area in which an exhaust gas quantity is small, so that the supercharging pressure can not follow the target quantity, which results in a state that the real air quantity does not temporarily reach the target air quantity. Due to the phenomenon, in the system in which the torque-based control is employed in the direct injection engine with the turbocharger, the following problems is likely to occur.
If the fuel leading type of torque-based control is employed, assuming that an intake air quantity is controlled to be its target value as described above, a fuel injection quantity is determined without obtaining information about an intake air quantity. Thus, in a state that a real air quantity does not temporarily reach a target air quantity, for example, in occurrence of a turbo lag, the fuel becomes relatively excessive and exhaust gas deteriorates. To address the problem, it seems effective to apply a transient correction (in which a quantity of fuel is reduced in accordance with phase of the air) to a fuel injection quantity by detecting or predicting occurrence of the turbo lag in order to prevent the fuel excess.
In addition, in the system in which the stoichiometric driving and the lean-burn driving can be switched in accordance with the driving states, it should be noted that a degree of the turbo lag varies in accordance with driving modes. That is, in the lean-burn driving, because a ratio of an intake air quantity to a fuel injection quantity is large and an exhaust gas quantity is also large, the turbine revolution number remains high even in a low revolution and low load area, so that a turbo lag is relatively small. Therefore, not only in the air leading type of torque-based control but also in the fuel leading type of torque-based control in which the fuel injection quantity is corrected (reduced) to prevent fuel excess by detecting or predicting occurrence of the above-described turbo lag, an accelerator response is preferable in the lean-burn driving in which the turbo lag is small, while the accelerator response is slow in the stoichiometric driving in which the turbo lag is large, so that a problem of making a driver feel uncomfortable occurs.
In addition, in the time of burning-switching for switching the stoichiometric driving and the lean-burn driving, the following problem occurs due to a turbo lag. Because a fuel quantity required for generating the same torque is different in the stoichiometric driving and in the lean-burn driving, a fuel correction is required in the time of switching. The fuel correction quantity depends primarily on pump loss, and the pump loss in the case of a turbo engine depends on not only a throttle opening but also a supercharging pressure. Therefore, in a transient time when the supercharging pressure continuously changes due to the turbo lag, the pump loss also changes continuously, and thus the fuel correction quantity is also required to be continuously changed correspondingly. However, in the prior art corresponding to a natural air intake engine such as shown in JP-A-10-47114, because the fuel correction quantity is set in consideration of only a steady driving state in which the pump loss remains constant, the fuel correction quantity is unsuitable in occurrence of the turbo lag so that there is a problem of resulting in a torque variation.
The present invention is provided in light of the above-described problems, and an object of the present invention is to prevent a torque variation, a change in torque characteristic, exhaust deterioration, or the like in a transient time, which occur due to a turbo lag, in a system in which a torque-base control is employed in a direct injection engine with a turbocharger and in which stoichiometric driving and lean-burn driving can be switched in accordance with driving states.
To achieve the object, according to the present invention, there are provided a fuel control apparatus of an engine and a method of controlling the fuel of the engine, in which a turbo lag index is computed on the basis of supercharging pressure information or air intake tube pressure information obtained directly or indirectly, so that a throttle opening or a fuel injection quantity is corrected on the basis of the above-described turbo lag index in order to obtain desired torque and exhaust characteristics.
Other objects, features, and advantages of the present invention will be apparent from description of embodiments of the present invention described below in reference to the accompanying drawing.
Now, the present invention will be described in detail in reference to the embodiments thereof.
Now, in reference to
Now, the turbo lag index computing means 214 and the transient time fuel correction quantity computing means 209, which are newly provided so as to correspond to a turbo engine and are important control blocks in the present invention, will be described. An object of these control blocks is to prevent the air-fuel ratio from being rich during acceleration and prevent a torque variation generated in switching between stoichiometric driving and lean driving, which are generated due to a turbo lag.
A specific computing content in the turbo lag index computing means 214 is as follows:
Turbo lag index=Supercharged pressure sensor output value/Target supercharged pressure
That is, in a steady condition, the turbo lag index is approximately 1, while in the case of a turbo lag occurrence condition, the index is calculated to be a value closer to 0 as a degree of the lag increases. On the basis of the turbo lag index, the transient time fuel correction quantity computing means 209 determines fuel correction quantities at a time of acceleration and burning-switching. Specific fuel correction contents at a time of the acceleration will be described in reference to
Now, a second embodiment according to the present invention will be illustrated in
Now, a third embodiment according to the present invention will be illustrated in
Now, a fourth embodiment according to the present invention will be described in reference to
For solving this problem, occurrence of a turbo lag is predicted in order to perform a throttle control so as to compensate the turbo lag in the stoichiometric running, and a normal throttle control is performed in the lean-burn running. This causes a difference between the torque characteristics in the stoichiometric running and the lean-burn running to be small, so that a preferable driveability can be obtained. It is contemplated that as a specific content for the throttle control in the above-described stoichiometric running, for example, a delay of an air quantity due to the turbo lag is approximated to a primary delay and compensation to the primary delay is performed using a differentiator. Alternatively, a real air quantity may be detected to perform a feedback control in which a throttle opening degree is determined in reference to a deviation between the real and target air quantities.
The target throttle opening degree computing means 211 incorporating this logic will be illustrated in
Although in the lean determination, the throttle opening degree is computed only by the base throttle opening degree computing part 402, in the stoichiometric determination, a value of the throttle opening degree transient time correction part 403 is added to the base throttle opening degree computing part 402 to obtain a target throttle opening degree.
The result in the case of employing the target throttle opening degree computing means 211 will be shown in
In addition, the problem is a common problem not only for the fuel leading torque-based control but also for the air leading torque-based control. Because the logic can also be employed in the air leading torque-based control, the problem that a torque characteristic in accelerator pushing-down varies between in stoichiometric running and in lean running can be solved by employing the logic.
Now, a fifth embodiment according to the present invention will be described in reference to
Although in the above-described embodiments, fuel correction computations in acceleration and in burning-switching is performed in the transient time fuel correction quantity computing means 209 which is modularized, the fuel correction computation may be directly performed in the target fuel quantity computing means 208 or the fuel efficiency correction computing means 207 as shown in
In addition, a fuel correction accuracy when switching the burning-states can further be increased by attaching an air intake pipe pressure sensor in the intake manifold 107 and using an air intake pipe pressure sensor output value 307 to estimate a pump loss transient change in the fuel efficiency correction computing means 207 as shown in
Further, a torque variation generated in switching between stoichiometric running and lean running is a common problem not only for the fuel leading torque-based control but also for the air leading torque-based control. Therefore, by applying this logic in which a pump loss transient change amount due to a turbo lag is estimated to perform a fuel correction, an effect of improving the torque variation is also expected for the air leading torque-based control.
As described above, according to the present invention, a torque variation, a change in torque characteristics, exhaust deterioration, or the like in a transient time, which occur due to a turbo lag, can be prevented in a system in which a torque-based control is employed in a direct injection engine with a turbocharger and switching between stoichiometric running and lean-burn running can be performed in accordance with the running states.
Although some embodiments have been described above, it is apparent to those skilled in the art that the present invention is not limited to these embodiments and various changes and modifications can be done in the spirit of the present invention and the scope of the appended claims.
Nakagawa, Shinji, Hori, Toshio, Satou, Shinya
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